Bug fix #2 Fixed critical bug and added regression tests

This case was found in #2

The position array Row.columnPos contained wrong values for the last column if the value is empty string. This caused panic or corrupt dump due to the wrong positions that were not overridden after previous COPY line parsing

internal/db/postgres/pgcopy/row.go

@@ -73,7 +73,7 @@ func (r *Row) Decode(raw []byte) error {
 
 	// Building column position slice
 	idx := 0
-	for colStartPos < len(raw) {
+	for colStartPos <= len(raw) {
 
 		colEndPos = slices.Index(raw[colStartPos:], DefaultCopyDelimiter)
 		if colEndPos == -1 {

internal/db/postgres/pgcopy/row_test.go

@@ -23,6 +23,80 @@ import (
 	"github.com/greenmaskio/greenmask/pkg/toolkit"
 )
 
+func TestDecode_positions_panic_error_regression(t *testing.T) {
+	// This case was found in https://github.com/GreenmaskIO/greenmask/issues/2
+	// Fixed bug:
+	// 	The position array Row.columnPos contained wrong values for the last column if the value is empty string
+	// 	This caused panic or corrupt dump due to the wrong positions that were not overridden after previous COPY line
+	//	parsing
+
+	type params struct {
+		record []byte
+	}
+
+	type expected struct {
+		positions []*columnPos
+		values    []string
+	}
+
+	type test struct {
+		name     string
+		params   params
+		expected expected
+	}
+
+	length := 4
+
+	tests := []test{
+		{
+			name: "not empty",
+			params: params{
+				record: []byte("27\t1213\t\tasda"),
+			},
+			expected: expected{
+				positions: []*columnPos{
+					{0, 2}, {3, 7}, {8, 8}, {9, 13},
+				},
+				values: []string{"27", "1213", "", "asda"},
+			},
+		},
+		{
+			name: "empty last two col",
+			params: params{
+				record: []byte("27\t12\t\t"),
+			},
+			expected: expected{
+				positions: []*columnPos{
+					{0, 2}, {3, 5}, {6, 6}, {7, 7},
+				},
+				values: []string{"27", "12", "", ""},
+			},
+		},
+	}
+
+	row := NewRow(length)
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := row.Decode(tt.params.record)
+			require.NoError(t, err)
+			require.Equal(t, len(tt.expected.positions), len(row.columnPos))
+
+			for idx, _ := range row.columnPos {
+				assert.Equalf(t, tt.expected.positions[idx].start, row.columnPos[idx].start, "wrong start value for idx %d", idx)
+				assert.Equalf(t, tt.expected.positions[idx].end, row.columnPos[idx].end, "wrong end value for idx %d", idx)
+			}
+
+			for idx, _ := range tt.expected.values {
+				v, err := row.GetColumn(idx)
+				require.NoErrorf(t, err, "unexpected error for idx %d", idx)
+				require.Falsef(t, v.IsNull, "unexpected NULL value for idx %d", idx)
+				require.Equalf(t, tt.expected.values[idx], string(v.Data), "unexpected value for idx %d", idx)
+			}
+		})
+	}
+}
+
 func TestDecode(t *testing.T) {
 
 	type result struct {